Esophageal cancer affects many patients worldwide. The percentage of males afflicted in particular has been increasing year by year. The prognosis for esophageal cancer is generally known to be very poor among the cancers of the gastrointestinal tract, including stomach and colon cancers. The treatment of esophageal cancer consists of a single treatment method or a combination of multiple treatment methods selected from among endoscopic treatment, surgery, radiation treatment, and chemotherapy, depending on the disease stage. Surgery, however, which is the most common treatment method is highly invasive and also carries a high risk of complications such as respiratory tract complications, recurrent nerve paralysis, and suture failure. Although the results of surgery have improved in recent years, the recurrence rate and mortality rate are still said to be high in comparison to other cancers of the gastrointestinal tract.
Early detection of esophageal cancer not only makes it possible to avoid highly invasive surgery and permits radical treatment by relatively less invasive endoscopic treatment and chemoradiation therapy, but can also be expected to improve the long-term prognosis thereafter. In addition, evaluation of the resection margin also becomes possible and residual-free treatment can be carried out if cancer tissue can be detected during surgery or endoscopic submucosal dissection (ESD). Given this background, the development of a method for detecting esophageal cancer quickly and accurately is strongly desired.
However, since early esophageal cancer is difficult to discover by ordinary endoscopic examination alone, iodine agents were often used in combination. The problem, however, was that they have strong symptoms of irritation such as heartburn and discomfort and cannot be used in patients with an iodine allergy.
On the other hand, dipeptidyl peptidase IV (DPP-IV), which is an enzyme that specifically removes a dipeptide from the N-end of proteins and polypeptides, is known to be related to many disease states. It was recently clarified that dipeptidyl peptidase IV is expressed at a higher level than in normal cells in esophageal cancer tissue (Non-Patent Reference 1).